Fifty years ago this July, Electricite de France began sealing off Normandy's La Rance estuary from the sea. After three years of work, the world's first large-scale tidal power plant was born. The station operates still, generating up to 240 megawatts of renewable power as the twice-daily tides force water in and out of the estuary through the hydroturbines seated within its 750-meter-long seawall.